Los Angeles County Sheriff Lee Baca said detectives will continue investigating the 25-year-old's death, but her remains may not offer many clues into how she died.
The skull and bones were discovered at about 1 p.m. Monday when park rangers were searching an abandoned marijuana grove near Malibu Canyon and Piuma roads in Malibu. The location was eight miles from the sheriff's station where Richardson had been released.
"I just am very, very disappointed that she's not alive," Baca said during a news conference.
Richardson vanished after being arrested last fall at a Malibu restaurant. She didn't have any money to pay her $89 dinner tab and was reportedly behaving in a bizarre way, so the manager called deputies to arrest her. She was held at sheriff's station and released with no way to get home.
Richardson's family has criticized the sheriff's department for releasing her at night from the rural sheriff's station without her car.
"It's just disheartening that our law enforcement agencies who are also here to protect us do not put forth effort to try to find us when we are in harm's way," said Richardson's mother, Latice Sutton.
The family has filed two lawsuits against the sheriff's department accusing it of negligence.
"We have nothing to hide in this case," Baca said. "The point is, there's a lot of factors beyond just the sheriff's department that need to be explained."
Family and friends said Richardson suffered from some kind of mental problem and argue that deputies should have had her evaluated before releasing her, especially since they had impounded her car, and she didn't have her purse or cell phone. Deputies also released her in the early morning hours when it was still dark.
"I tried to fight for her as long as I could," said Richardson's father, Michael Richardson. "What I have to do is get back, and get emotionally strong because I have more fighting to do.
"I'm deeply hurt," he went on to say. "I knew I was fighting a losing battle, but I so wanted the outcome to be different."
Over the last year, the sheriff's department conducted widespread searches, even going to Las Vegas on a report that she may have been spotted there.
An official report says deputies acted reasonably in releasing Richardson. The county's Office of Independent Review said deputies carefully determined she wasn't drunk, dangerous or mentally ill before freeing her.
The previously confidential July report made public Thursday also says the woman refused offers to remain jailed until daybreak or until she could get a ride.
Community leaders are now calling for an FBI investigation.
"We still don't know why Mitrice Richardson is dead, how it happened, and more importantly, why it happened," said Earl Ofari Hutchinson of the Urban Policy Roundtable. "We know one thing: It shouldn't have happened."
On Thursday, Richardson said he will push for a law requiring the sheriff's department to provide a taxi voucher to anyone who needs a safe ride home.
The Associated Press and City News Service contributed to this report.